Cr2O3 + 9 KNO3 + 4 KOH → 2 K2CrO7 + 9 KNO2 + 2 H2O
This is an oxidation-reduction (redox) reaction:
9 NV + 18 e- → 9 NIII (reduction)
2 CrIII - 18 e- → 2 CrXII (oxidation)
KNO3 is an oxidizing agent, Cr2O3 is a reducing agent.
Warning: Unknown compound 'K2CrO7'